System and method for actuating an engine valve

ABSTRACT

An engine valve actuation system is provided that includes an engine valve that is movable between a first position where the engine valve prevents a flow of fluid and a second position where the engine valve allows a flow of fluid. A cam assembly is operatively connected to the engine valve to move the engine valve between the first position and the second position in a predetermined actuation pattern. A valve actuator having a piezo electric device is operable to change the movement of the engine valve from the predetermined actuation pattern. A controller is adapted to control the piezo electric device to achieve a desired valve actuation pattern.

This is a continuation of application Ser. No. 10/673,241, filed Sep.30, 2003, now U.S. Pat. No. 6,935,287 which is incorporated herein byreference.

TECHNICAL FIELD

The disclosed invention is directed to a system and method for actuatingan engine valve and, more particularly, to a system and method forcontrolling an engine valve actuator having a piezo electric device.

BACKGROUND

The operation of an internal combustion engine, such as, for example, adiesel, gasoline, or natural gas engine, may cause the generation ofundesirable emissions. These emissions, which may include particulatesand oxides of nitrogen (NOx), are generated when fuel is combusted in acombustion chamber of the engine. An exhaust stroke of an engine pistonforces exhaust gas, which may include these emissions, from the engine.If no emission reduction measures are in place, these undesirableemissions will eventually be exhausted to the environment.

Research is currently being directed towards decreasing the amount ofundesirable emissions that are exhausted to the environment during theoperation of an engine. It is expected that improved engine design andimproved control over engine operation may lead to a reduction in thegeneration of undesirable emissions. Many different approaches such as,for example, engine gas recirculation and aftertreatments, have beenfound to reduce the amount of emissions generated during the operationof an engine. Unfortunately, the implementation of these emissionreduction approaches typically results in a decrease in the overallefficiency of the engine.

Additional efforts are being focused on improving engine efficiency tocompensate for the efficiency loss due to the emission reductionsystems. One such approach to improving the engine efficiency involvesadjusting the actuation pattern of the engine valves. For example, theactuation pattern of the intake and exhaust valves may be modified toimplement a variation on the typical diesel or Otto cycle known as theMiller cycle. In a “late intake” type Miller cycle, the intake valves ofthe engine are held open during a portion of the compression stroke ofthe piston. Implementing a pattern variation, such as the late-intakeMiller cycle, may improve the overall efficiency of the engine.

The engine valves in an internal combustion engine are typically drivenby a cam arrangement that is operatively connected to the crankshaft ofthe engine. The rotation of the crankshaft results in a correspondingrotation of a cam that drives one or more cam followers. The movement ofthe cam followers results in the actuation of the engine valves. Theshape of the cam governs valve lift during valve actuation. Therelationship of valve lift to cam angle, as dictated by the shape of thecam, creates a predetermined engine valve actuation pattern as the camis rotated.

An engine valve actuation system may include a hydraulic actuator thatis adapted to vary the valve actuation pattern established by the shapeof the cam. For example, as described in U.S. Pat. No. 6,237,551 toMacor et al., issued on May 29, 2001, an engine valve actuation systemmay include a hydraulic actuator that establishes a hydraulic linkbetween the cam and the intake valve. When the link is established, thevalve will be actuated according to the shape of the cam to produce apredetermined valve actuation pattern of valve opening and valveclosing. However, when the hydraulic link is broken, such as by openinga control valve, the force of a valve return spring causes the enginevalve to close. Thus, breaking the hydraulic link allows the enginevalve to move through an actuation pattern different from thepredetermined pattern that would be achieved by the shape of the cam.

However, the operational performance of the hydraulic actuator maydepend upon the viscosity of the operating fluid. When the operatingfluid is cold, such as when the engine is starting, the hydraulicactuator may experience slow response times. The slow response times maylead to the engine experiencing rough running conditions or difficultystarting until the operating fluid is warmed enough to allow thehydraulic actuator to operate properly. Depending upon the currentenvironmental conditions, the engine may need to operate for a period oftime to warm the operating fluid so that the hydraulic actuator willoperate as expected.

In addition, a hydraulic actuator, such as described in the '551 patentto Macor, may not be able to actuate the engine valve independently ofthe cam assembly. The force exerted by the engine valve springs may beinsurmountable with a hydraulic actuator that is limited by the pressureand velocity of fluid supplied by a low pressure fluid supply system. Anincrease in the demand for force or response time could requireadditional capacity of the fluid source, typically resulting in anincrease in the cost of the engine as well as a decrease in overallefficiency of the engine.

The engine valve actuation system of the disclosed invention solves oneor more of the problems set forth above.

SUMMARY OF THE INVENTION

In one aspect, the disclosed invention is directed to an engine valveactuation system that includes an engine valve that is movable between afirst position where the engine valve prevents a flow of fluid and asecond position where the engine valve allows a flow of fluid. A camassembly is operatively connected to the engine valve to move the enginevalve between the first position and the second position in apredetermined actuation pattern. A valve actuator having a piezoelectric device is operable to change the movement of the engine valvefrom the predetermined actuation pattern. A controller is adapted tocontrol the piezo electric device to achieve a desired valve actuationpattern.

In another aspect, the disclosed invention is directed to a method ofactuating an engine valve. A cam assembly is operated to move an enginevalve in a predetermined pattern between a first position where theengine valve blocks a flow of fluid and a second position where theengine valve allows a flow of fluid. A valve actuator having a piezoelectric device is operated to selectively engage the engine valve. Thepiezo electric device of the valve actuator is controlled to achieve adesired valve actuation pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional view of an exemplary embodimentof an internal combustion engine;

FIG. 2 is a diagrammatic cross-sectional view of a cylinder and valveactuation assembly in accordance with an exemplary embodiment of thedisclosed invention;

FIG. 3 is a schematic and diagrammatic illustration of an actuator foran engine valve in accordance with an exemplary embodiment of thedisclosed invention;

FIG. 4 is a schematic and diagrammatic illustration of an actuator foran engine valve in accordance with an exemplary embodiment of thedisclosed invention;

FIG. 5 is a schematic and diagrammatic illustration of an actuator foran engine valve in accordance with an exemplary embodiment of thedisclosed invention;

FIG. 6 is a schematic and diagrammatic illustration of an actuator foran engine valve in accordance with an exemplary embodiment of thedisclosed invention;

FIG. 7 is a schematic and diagrammatic illustration of an actuator foran engine valve in accordance with an exemplary embodiment of thedisclosed invention;

FIG. 8 is a schematic and diagrammatic illustration of an actuator foran engine valve in accordance with an exemplary embodiment of thedisclosed invention; and

FIG. 9 is a graphic illustration of an exemplary valve actuation as afunction of engine crank angle for an engine operating in accordancewith the disclosed invention.

DETAILED DESCRIPTION

An exemplary embodiment of an internal combustion engine 20 isillustrated in FIG. 1. For the purposes of the present disclosure,engine 20 is depicted and described as a four stroke diesel engine. Oneskilled in the art will recognize, however, that engine 20 may be anyother type of internal combustion engine, such as, for example, agasoline or natural gas engine.

As illustrated in FIG. 1, engine 20 includes an engine block 28 thatdefines a plurality of cylinders 22. A piston 24 is slidably disposedwithin each cylinder 22. In the illustrated embodiment; engine 20includes six cylinders 22 and six associated pistons 24. One skilled inthe art will readily recognize that engine 20 may include a greater orlesser number of pistons 24 and that pistons 24 may be disposed in an“in-line” configuration, a “V” configuration, or any other conventionalconfiguration.

As also shown in FIG. 1, engine 20 includes a crankshaft 27 that isrotatably disposed within engine block 28. A connecting rod 26 connectseach piston 24 to crankshaft 27. Each piston 24 is coupled to crankshaft27 so that a sliding motion of piston 24 within the respective cylinder22 results in a rotation of crankshaft 27. Similarly, a rotation ofcrankshaft 27 will result in a sliding motion of piston 24.

Engine 20 also includes a cylinder head 30. Cylinder head 30 defines anintake passageway 41 that leads to at least one intake port 36 for eachcylinder 22. Cylinder head 30 may further define two or more intakeports 36 for each cylinder 22.

An intake valve 32 is disposed within each intake port 36. Intake valve32 includes a valve element 40 that is configured to selectively blockintake port 36. As described in greater detail below, each intake valve32 may be actuated to move or “lift” valve element 40 to thereby openthe respective intake port 36. In a cylinder 22 having a pair of intakeports 36 and a pair of intake valves 32, the pair of intake valves 32may be actuated by a single valve actuation assembly or by a pair ofvalve actuation assemblies.

Cylinder head 30 also defines at least one exhaust port 38 for eachcylinder 22. Each exhaust port 38 leads from the respective cylinder 22to an exhaust passageway 43. Cylinder head 30 may further define two ormore exhaust ports 38 for each cylinder 22.

An exhaust valve 34 is disposed within each exhaust port 38. Exhaustvalve 34 includes a valve element 48 that is configured to selectivelyblock exhaust port 38. As described in greater detail below, eachexhaust valve 34 may be actuated to move or “lift” valve element 48 tothereby open the respective exhaust port 38. In a cylinder 22 having apair of exhaust ports 38 and a pair of exhaust valves 34, the pair ofexhaust valves 34 may be actuated by a single valve actuation assembly44 or by a pair of valve actuation assemblies 44.

FIG. 2 illustrates an exemplary embodiment of one cylinder 22 of engine20. As shown, cylinder head 30 defines a pair of intake ports 36connecting intake passageway 41 to cylinder 22. Each intake port 36includes a valve seat 50. One intake valve 32 is disposed within eachintake port 36. Valve element 40 of intake valve 32 is configured toengage valve seat 50. When intake valve 32 is in a closed position,valve element 40 engages valve seat 50 to close intake port 36 and blockfluid flow relative to cylinder 22. When intake valve 32 is lifted fromthe closed position, intake valve 32 allows a flow of fluid relative tocylinder 22.

Similarly, cylinder head 30 may define two or more exhaust ports 38(only one of which is illustrated in FIG. 1) that connect cylinder 22with exhaust passageway 43. One exhaust valve 34 is disposed within eachexhaust port 38. A valve element 48 of each exhaust valve 34 isconfigured to close exhaust port 38 when exhaust valve 34 is in a closedposition and block fluid flow relative to cylinder 22. When exhaustvalve 34 is lifted from the closed position, exhaust valve 32 allows aflow of fluid relative to cylinder 22.

As also shown in FIG. 2, a valve actuation assembly 44 is operativelyassociated with intake valves 32. Valve actuation assembly 44 includes abridge 54 that is connected to each valve element 40 through a pair ofvalve stems 46. A spring 56 may be disposed around each valve stem 46between cylinder head 30 and bridge 54. Spring 56 acts to bias bothvalve elements 40 into engagement with the respective valve seat 50 tothereby close each intake port 36.

Valve actuation assembly 44 also includes a rocker arm 64. Rocker arm 64is configured to pivot about a pivot 66. One end 68 of rocker arm 64 isconnected to bridge 54. The opposite end of rocker arm 64 is connectedto a cam assembly 52. In the exemplary embodiment of FIG. 2, the camassembly 52 includes a cam 60 having a cam lobe 63 and mounted on acamshaft 65, a push rod 61, and a cam follower 62. One skilled in theart will recognize that cam assembly 52 may have other configurations,such as, for example, where cam 60 acts directly on rocker arm 64.

Valve actuation assembly 44 may be driven by cam 60. The shape of cam 60governs valve lift during valve actuation. The relationship of valvelift to cam angle as dictated by the shape of the cam 60, creates apredetermined engine valve actuation pattern as the cam 60 is rotated.

Cam 60 is connected to crankshaft 27 so that a rotation of crankshaft 27induces a corresponding rotation of cam 60. Cam 60 may be connected tocrankshaft 27 through any means readily apparent to one skilled in theart, such as, for example, through a gear train assembly (not shown). Asone skilled in the art will recognize, a rotation of cam 60 will causecam follower 62 and associated push rod 61 to periodically reciprocatebetween an upper and a lower position.

The reciprocating movement of push rod 61 causes rocker arm 64 to pivotabout pivot 66. When push rod 61 moves in the direction indicated byarrow 58, rocker arm 64 will pivot and move bridge 54 in the oppositedirection. The movement of bridge 54 causes each intake valve 32 to liftand open intake ports 36. As cam 60 continues to rotate, springs 56 willact on bridge 54 to return each intake valve 32 to the closed position.

In this manner, the shape and orientation of cam 60 actuates intakevalves 32 in a predetermined pattern. Because cam assembly 52 isconnected to crankshaft 27, the timing of the predetermined intake valveactuation pattern may be synchronized with the motion of the associatedengine piston 24. For example, intake valves 32 may be actuated to openintake ports 36 when piston 24 is moving from a top-dead-center positiontowards a bottom-dead-center position in an intake stroke to allow airto flow from intake passageway 41 into cylinder 22.

A similar valve actuation assembly may be connected to exhaust valves34. A second cam (not shown) may be connected to crankshaft 27 toactuate exhaust valves 34 in a predetermined actuation pattern. Thetiming of the predetermined exhaust valve actuation pattern may also besynchronized with the motion of the associated engine piston 24. Forexample, exhaust valves 34 may be actuated to open exhaust ports 38 whenpiston 24 is moving from a bottom-dead-center position towards atop-dead-center position to allow exhaust to flow from cylinder 22 intoexhaust passageway 43.

As also shown in FIG. 2, valve actuation assembly 44 may include anactuator 70. Actuator 70 includes a housing 72 that defines a bore 80. Apiston 74 having an end 75 may be slidably disposed in bore 80.

Housing 72 of actuator 70 may be connected to cylinder head 30. Forexample, a pair of supports 81 may extend from housing 72 to cylinderhead 30. Supports 81 may be attached to cylinder head 30 by anyconnecting member readily apparent to one skilled the art. For example,bolts 83 may connect supports 81 to cylinder head 30.

Housing 72 may be disposed on cylinder head 30 to allow end 75 of piston74 to operatively engage intake valves 32. In the illustratedembodiment, end 75 of piston 74 may selectively engage end 68 of rockerarm 64. One skilled in the art will recognize, however, that end 75 ofpiston 74 may engage another portion of rocker arm 64 or end 75 ofpiston 74 may be operatively engaged with intake valves 32 in anotherway, such as, for example, through a direct connection with intakevalves 32.

Actuator 70 may include one or more piezo electric devices 78, 89, asshown in FIGS. 3–8, that are adapted to control the motion of piston 74relative to bore 80. Piezo electric devices 78, 89 may include one ormore columns of piezo electric crystals. Piezo electric crystals arestructures with random domain orientations. These random orientationsare asymmetric arrangements of positive and negative ions that exhibitpermanent dipole behavior. When an electric field is applied to thecrystals, such as, for example, by the application of a voltage, thepiezo electric crystals expand along the axis of the electric field asthe domains line up. As illustrated in the exemplary embodiments ofFIGS. 3–8, one or more piezo electric devices may be utilized in anumber of different configurations to control the motion of piston 74relative to bore 80.

For example, in the embodiment of FIG. 3, the piezo electric device 78includes a column of crystals 111 having one end 112 that is securelyfixed to actuator housing 72. A piston 116 is operably attached to theother end 114 of the piezo crystal column 111. Piston 116 may beslidably disposed within bore 117 of actuator housing 72. Bore 117 maycontain a supply of hydraulic fluid that is in fluid communication withpiston 74 by means of a passageway 86.

A voltage may be applied to the column of crystals 111 in piezo electricdevice 78 to cause column of crystals 111 to expand along an axis ofbore 117. The expansion of column of crystals 111 moves piston 116 adistance into bore 117, thereby increasing the pressure of the fluid inbore 117 and in passageway 86. The pressurized fluid in passageway 86flows into bore 80 and acts to move piston 74 in the direction indicatedby arrow 77 and into engagement with rocker arm 64.

Piezo electric device 78 may be activated to move the associated intakevalves 32 from the first position to the second position or piezoelectric device 78 may be activated to prevent the associated intakevalves 32 from moving from the second position to the first position.Piezo electric device 78 may be activated to engage piston 74 withrocker arm 64 when intake valves 32 are in the first position to movethe intake valves 32 from the first position to the second position.Alternatively, piezo electric device 78 may be activated to engagepiston 74 with rocker arm 64 when intake valves 32 are in the secondposition or are moving from the second position towards the firstposition. With either approach, piezo electric device 78 may beactivated to vary the actuation pattern of the intake valves 32 from thepredetermined actuation pattern dictated by the shape and orientation ofcam 60.

Actuator 70 may include one or more seals that prevent fluid fromleaking from the actuator housing 72. For example, a seal 73 may bedisposed between piston 74 and bore 80. In addition, a second seal 118may be disposed between piston 116 and bore 117. Seal 73 and seal 118may be any type of sealing element adapted to prevent fluid fromescaping from bore 80 past piston 74 or from bore 117 past piston 116.

As shown in FIG. 4, valve actuator 70 may also include a second piezoelectric device 89. Second piezo electric device 89 may also include acolumn of crystals 111. One end 112 of column of crystals 111 may befixed to actuator housing 72 and piston 116 may be connected to theother end of column of crystals 111. Second piezo electric device 89 maybe in fluid connection with bore 80 by a fluid passageway 88. Theapplication of a voltage to second piezo electric device 89 may causethe expansion of column of crystals 111 and the pressurization of fluidin fluid passageway 88. In this manner, second piezo electric device 89may exert a force on piston 74 in an opposing direction to the forceexerted by first piezo electric device 78. In this manner second piezodevice 89 may act in conjunction with valve spring 56 to exert a forceon piston 74 and associated intake engine valve 32 or exhaust enginevalve 34 to move piston 74 in a direction opposite to the movementinitiated by first piezo device 78.

Alternatively, as shown in the embodiment of FIG. 5, a mechanicalbiasing means may be disposed in bore 80. The mechanical biasing meansacts on piston 74 to bias piston 74 away from housing 72, i.e. in thedirection of arrow 77. The mechanical biasing means may be anymechanical biasing element, such as, for example, a spring 76, that isadapted to bias piston 74 with respect to housing 72. The force exertedby mechanical biasing means may be less than the force exerted bysprings 56 (referring to FIG. 2) on bridge 54.

Actuator 70 may also receive operating fluid from a common source. Forexample, as also shown in FIG. 5, a fluid supply system 97 may supplyoperating fluid to actuator 70 through fluid line 95. Fluid supplysystem 97 may include a source of fluid 93, that draws fluid from a tank94 holding a supply of fluid, which may be, for example, a hydraulicfluid, a lubricating oil, a transmission fluid, or fuel. Source of fluid93 may increase the pressure of the fluid and direct the fluid intoactuator 70. Source of fluid 93 and fluid line 95 may be part of alubrication system, such as typically accompanies an internal combustionengine. Fluid line 95 may contain pressurized fluid having a pressureof, for example, less than 700 kPa (100 psi) or, more particularly,between about 210 kPa and 620 kPa (30 psi and 90 psi). Alternatively,the source of hydraulic fluid may be a pump configured to provide fluidat a higher pressure, such as, for example, between about 10 MPa and 35MPa (1450 psi and 5000 psi).

One skilled in the art will recognize that fluid supply system 97 mayhave a variety of different configurations and include a variety ofdifferent components. For example, a snubbing valve 79 may be disposedin fluid line 95 between bore 80 and control valve 82. Snubbing valve 79may be configured to decrease the rate at which fluid exits bore 80 tothereby slow the rate at which piston 74 moves within bore 80. A dampingsystem may also be implemented that prevents pressure oscillations inactuator 70, which may include an accumulator 71 and a restrictedorifice 67 as in FIG. 5. One or more check valves may be included. Acheck valve 98, for example, may be disposed in line 95, between source93 and actuator 70 as seen in FIGS. 5 and 6.

A seal 73 may be disposed between piston 74 and bore 80. Seal 73 may beany type of sealing element adapted to prevent fluid from escaping frombore 80 past piston 74.

Housing 72 may further define fluid passageway 95 to connect tank 94with bore 80. Fluid passageway 95 provides a fluid connection thatallows fluid to flow between tank 94 and bore 80. For example, fluid mayflow from tank 94 to bore 80 as spring 76 biases piston 74 away fromhousing 72. In addition, fluid may flow from tank 94 to bore 80 asrocker arm 64 (referring to FIG. 2) pivots away from actuator 70 tothereby move piston 74 to follow the motion of rocker arm 64.

As shown in FIGS. 5–6, a control valve 82 may be positioned in a fluidline 99 between bore 80 and tank 94. Control valve 82 may be movedbetween a first position where fluid is allowed to flow through fluidpassageways 95 and 99 and a second position where fluid is preventedfrom flowing through fluid passageways 95 and 99. Control valve 82 maybe moved to the second position to prevent fluid from flowing from bore80 to thereby prevent piston 74 from moving relative to bore 80.

As shown in the embodiments of FIGS. 5–6, piezo electric device 78 maybe operably connected to control valve 82. Piezo electric device 78 maybe arranged such that one end 112 is securely fixed to actuator housing72 and column of crystals 111 extends away from fixed end 112 in asubstantial alignment with control valve 82. The other end 114 of columnof crystals 111 may be operably connected to control valve 82. A voltagemay be applied to piezo electric device 78 to expand column of crystals111 to cause an opening movement of control valve 82. In this manner,piezo electric device 78 may be operated to allow a flow of fluid frombore 80 to tank 94.

As shown in FIG. 5, control valve 82 may include a return spring 109that acts to close control valve 82. The closing of control valve 82stops the flow of fluid from bore 80 and thereby prevents piston 74 frommoving relative to bore 80. Control valve 82 may be closed when piston74 is extended relative to actuator housing 72. In this position, piston74 may engage rocker arm 64 (referring to FIG. 2) when intake valves 32are moving from the second position to the first position. Theengagement of the piston 74 with the rocker arm 64 prevents intakevalves 32 from moving to the first, or closed position. In this manner,the expansion of the piezo electric device 78 may be controlled tocontrol the motion of piston 74 and thereby change the predeterminedvalve actuation pattern of the intake valves 32.

In addition, as shown in FIG. 6, second piezo electric device 89 may beused to close control valve 82. Column of crystals 111 in second piezoelectric device 89 may be disposed between actuator housing 72 andcontrol valve 82. Piezo electric device 89 may be activated to expandcolumn of crystals 111 in an opposing direction to piezo electric device78 to thereby move control valve 82 to the closed position to preventpiston 74 from moving relative to bore 80.

Alternatively, as shown in the embodiment of FIG. 7, piezo electricdevice 78 may be arranged within valve actuator 70 to act directly onpiston 74.

For example, first end 112 of piezo electric device 78 may be securelyfixed to actuator housing 72 and column of crystals 111 may extend awayfrom fixed end 112 and into bore 80. Second end 114 of column ofcrystals 111 is operably connected to piston 74. The activation of piezoelectric device 78 may therefore exert a direct force on piston 74. Asdescribed previously, piezo electric device 78 may be activated toengage piston 74 with rocker arm 64 when the associated intake valves 32are in either the first position or the second position to therebychange the predetermined valve actuation pattern.

As shown in FIG. 8, second piezo electric device 89 may be disposedbetween actuator housing 72 and piston 74. Second piezo electric device89 may be activated to exert a force on piston 74 in an opposingdirection to the force exerted by first piezo electric device 78. Secondpiezo device 89 may act in conjunction with valve spring 56 to exert aforce on piston 74 and associated intake engine valve 32 or exhaustengine valve 34 to move piston 74 in a direction opposite to themovement initiated by first piezo device 78.

It should be noted that, while the embodiments of valve actuator 70 havebeen described in connection with intake valves 32, a valve actuator 70may also be associated with the exhaust valves 34 of a particular enginecylinder 22 (referring to FIG. 1). Thus, the described valve actuatormay be used to vary the predetermined valve actuation timing of intakevalves 32 and/or exhaust valves 34.

As shown in FIG. 1, a controller 100 may be connected to valve actuator70 in each valve actuation assembly 44. Controller 100 may include anelectronic control module that has a microprocessor and a memory. As isknown to those skilled in the art, the memory is connected to themicroprocessor and stores an instruction set and variables. Associatedwith the microprocessor and part of the electronic control module arevarious other known circuits such as, for example, power supplycircuitry, signal conditioning circuitry, and solenoid driver circuitry,among others.

As shown in FIG. 2, engine 20 may include a position sensor 122associated with the engine valve 32 and in communication with controller100 through lead 124. The position sensor 122 may be any type ofposition sensor known in the art such as, for example, a piezo crystalposition sensor. A piezo crystal position sensor includes a piezocrystal that exerts a voltage proportional to the compression of thecrystal.

The position sensor may be adapted to provide an indication of theposition of the engine valve 32 to thereby monitor the lift height ofthe engine valve 32. In the embodiment of FIG. 2, the position sensor122 is engaged with bridge 54. Alternatively, the position sensor 122may be engaged directly to the engine valve 32, to the piston 74, or tothe control valve 82.

Controller 100 may be programmed to control one or more aspects of theoperation of engine 20. For example, controller 100 may be programmed toreceive signals from the position sensor 122 indicative of valveposition and control the valve actuation assembly based on the valveposition. The controller may also be programmed to control the fuelinjection system and any other function readily apparent to one skilledin the art. Controller 100 may control engine 20 based on the currentoperating conditions of the engine and/or instructions received from anoperator. As shown in FIGS. 3–8, controller 100 is connected to piezoelectric devices 78 and 89 in actuator housing 72 through a lead 101.

Controller 100 may be further programmed to receive information from oneor more sensors operatively connected with engine 20. Each of thesensors may be configured to sense one or more operational parameters ofengine 20. One skilled in the art will recognize that many types ofsensors may be used in conjunction with engine 20. For example, engine20 may be equipped with sensors configured to sense one or more of thefollowing: the temperature of the engine coolant, the temperature of theengine, the ambient air temperature, the engine speed, the load on theengine, the intake air pressure, the position of the piston relative tothe cylinder, and the pressure in the cylinder.

Engine 20 may be further equipped with a sensor configured to monitorthe crank angle of crankshaft 27 to thereby determine the position ofpistons 24 within their respective cylinders 22. The crank angle ofcrankshaft 27 is also related to actuation patterns of intake valves 32and exhaust valves 34. An exemplary graph 102 indicating therelationship between valve actuation pattern and crank angle isillustrated in FIG. 9. As shown by graph 102, the exhaust valve lift 104is timed to substantially coincide with the exhaust stroke of piston 24and the intake valve lift 106 is timed to substantially coincide withthe intake stroke of piston 24.

INDUSTRIAL APPLICABILITY

Based on information provided by the engine sensors, controller 100 mayoperate piezo electric device 78 and/or 89 in each valve actuationassembly 44 to change the actuation pattern of the intake and/or exhaustvalves 32, 34 of engine 20 from the predetermined actuation pattern to adesired actuation pattern. For example, under certain operatingconditions, controller 100 may implement a late intake Miller cycle ineach cylinder 22 of engine 20. Under normal operating conditions,implementation of the late intake Miller cycle may increase the overallefficiency of the engine 20. However, under some operating conditions,such as, for example, when engine 20 is cold, controller 100 may operateengine 20 on a conventional diesel cycle.

The following discussion describes a valve actuation pattern controlthat results in the implementation of a late intake Miller cycle in asingle cylinder 22 of engine 20. One skilled in the art will recognizethat the disclosed system may be used to selectively implement a lateintake Miller cycle in all cylinders of engine 20 in the same or asimilar manner. In addition, the disclosed system may be used toimplement other valve actuation variations on the conventional dieselcycle, such as, for example, a late exhaust closing 119 (see FIG. 9)used for an exhaust gas re-circulation event, where exhaust valves 34have a late closing during the intake stroke, an engine brake valveevent 120 (see FIG. 9), where the exhaust valves 34 are opened duringthe peak of the compression stroke, or any other such timing variationthat may be apparent to one skilled in the art.

Controller 100 may implement a late intake valve closing Miller cyclefor a particular cylinder 22 by controlling the piezo electric device 78in valve actuator 70. The rotation of cam 60 causes rocker arm 64 topivot to thereby actuate intake valves 32 in a predetermined pattern.The predetermined pattern may cause intake valves 32 to move from thefirst position to the second position to coincide with a certainposition of the associated engine piston 24.

In the embodiments of FIGS. 3–8, controller 100 may send a signal, suchas, for example, a voltage having a certain magnitude, to activate piezoelectric device 78 and thereby extend piston 74 in the direction ofarrow 77 (referring to FIG. 2). The signal may be adapted to move piston74 to a certain position where engagement with normal rocker arm 64movement is initiated. As cam 60 continues to rotate, springs 56 urgeintake valves 32 towards their closed position until end 68 of rockerarm 64 engages end 75 of piston 74 where piston 74 prevents intakevalves 32 from closing. As long as piston 74 remains in the extendedposition, piston 74 will prevent springs 56 from returning intake valves32 to the closed position. Thus, piezo electric device 78 will holdintake valves 32 in the open position, independent of the action of camassembly 52.

Controller 100 may close intake valves 32 by sending a signal to piezoelectric device 78, such as by removing the voltage applied to piezoelectric device 78, thereby allowing crystal column 111 to compress ormove towards its original position. In the embodiments of FIGS. 3, 5, 6and 7, valve springs 56 may then act to move piston 74 away from itsextended position. Alternatively, in the embodiments of FIGS. 4 and 8,second piezo device 89 may be activated to move piston 74 away from itsextended position. This allows rocker arm 64 to pivot so that intakevalves 32 are moved to the closed position.

An exemplary late intake closing 108 is compared in FIG. 9 to a closing110 of the predetermined action pattern produced by the rotation of cam60. As shown, the intake valve actuation 106 is extended into a portionof the compression stroke of piston 24. This allows some of the air incylinder 22 to escape as piston 24 begins the compression stroke. Theamount of air allowed to escape cylinder 22 may be controlled byadjusting the crank angle at which piston 74 exerts interfering pressureon rocker arm 64. Piston 74 may be engaged at an earlier crank angle todecrease the amount of escaping air or at a later crank angle toincrease the amount of escaping air.

Certain operating conditions may require that engine 20 be operated on aconventional diesel cycle instead of the late intake Miller cycledescribed above. These types of operating conditions may be experienced,for example, when engine 20 is first starting or is otherwise operatingunder cold conditions. The described valve actuation system 44 allowsfor the selective disengagement of the late intake Miller cycle.

Controller 100 may disengage the late intake Miller cycle by controllingthe piezo electric device 78 so as not to force the piston to applypressure against rocker arm 64. If piezo device 78 is not causing piston74 to apply pressure against rocker arm 64, intake valves 32 will not beblocked from returning to the closed position. Thus, the actuation ofintake valves 32 will be driven by the shape of cam 60.

Thus, when piston 74 does not apply pressure against rocker arm 64,intake valves 32 will follow a conventional diesel cycle as governed bycam 60. As shown in FIG. 9, intake valve actuation 106 will follow aconventional closing 110. In the conventional closing 110, the closingof intake valves 32 substantially coincides with the end of the intakestroke of piston 24. When intake valves 32 close at the end of theintake stroke, no air will be forced from cylinder 22 during thecompression stroke. This results in piston 24 compressing the fuel andair mixture to a higher pressure, which will facilitate diesel fuelcombustion. This is particularly beneficial when engine 20 is operatingin cold conditions.

As will be apparent from the foregoing description, the described systemprovides an engine valve actuation system that may selectively alter thepattern of the intake and/or exhaust valve actuation of an internalcombustion engine. The actuation of the engine valves may be based onsensed operating conditions of the engine. For example, the engine valveactuation system may implement a late intake Miller cycle when theengine is operating under normal operating conditions. The late intakeMiller cycle may be disengaged when the engine is operating underadverse operating conditions, such as when the engine is cold. Thus, thedisclosed system and method provide a flexible engine valve actuationsystem that provides for a variety of enhanced performance capabilitiesand fuel efficiency gains.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the described engine valveactuation system without departing from the scope of the invention.Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope of theinvention being indicated by the following claims and their equivalents.

1. An engine valve actuation system, comprising: an engine intake valvemovable between a first position where the engine intake valve preventsa flow of fluid and a second position where the engine intake valveallows a flow of fluid; a cam assembly operatively connected to theengine intake valve to move the engine intake valve between the firstposition and the second position in a predetermined actuation pattern; avalve actuator having a piezo electric device, and being operable tochange the movement of the engine intake valve from the predeterminedactuation pattern by pressurizing a fluid passageway by the piezoelectric device; and a controller adapted to control the piezo electricdevice to achieve a desired valve actuation pattern.
 2. The valveactuation system of claim 1, wherein the valve actuator furtherincludes: an actuator housing defining a bore; and a piston slidablydisposed in the bore of the actuator housing and adapted to engage theengine intake valve, wherein the piston is configured to be moved by thepressurizing of the fluid passageway.
 3. The valve actuation system ofclaim 2, further including a second fluid passageway pressurized by asecond piezo electric device arranged such that force generated by thesecond piezo electric device opposes movement caused by the first piezoelectric device to move the piston in a direction opposite the movementinitiated by the first piezo electric device.
 4. The valve actuationsystem of claim 1, further including: an actuator housing defining abore; and a piston slidably disposed in the bore of the actuatorhousing, the piston adapted to move between a first position and asecond position where the piston moves into operative connection withthe engine valve.
 5. The valve actuation system of claim 4, furtherincluding a snubbing valve adapted to slow a seating velocity of thepiston.
 6. The valve actuation system of claim 4, further including: asource of the fluid; an accumulator disposed in the actuator housing,the accumulator in fluid connection with the source of fluid and thebore; a restrictive orifice disposed at the inlet to the accumulator;and a check valve disposed in the fluid line between the source of fluidand the actuator housing.
 7. The valve actuation system of claim 4,further including a mechanical biasing element acting on the piston tomove the piston towards the second position.
 8. The valve actuationsystem of claim 4, further including a second opposing piezo electricdevice for moving the piston in a direction opposite the movementinitiated by the first piezo electric device.
 9. The valve actuationsystem of claim 1, further including a position sensor operable to sensethe position of the engine valve.
 10. A method of actuating an enginevalve, comprising: operating a cam assembly to move an engine intakevalve in a predetermined actuation pattern between a first positionwhere the engine valve blocks a flow of fluid and a second positionwhere the engine valve allows a flow of fluid; operating a valveactuator having at least one piezo electric device, the valve actuatoradapted to change the movement of the engine intake valve from thepredetermined actuation pattern; pressurizing a fluid with the at leastone piezo electric device; and controlling the at least one piezoelectric device to achieve a desired valve actuation pattern.
 11. Themethod of claim 10, including: directing the pressurized fluid to apiston which engages the engine valve.
 12. The method of claim 10,further including extending a piston from an actuator housing toselectively engage the engine intake valve.
 13. The method of claim 12,including: directing a flow of fluid from a source into a bore in theactuator housing associated with the piston; and applying a voltage tothe piezo electric device to pressurize fluid in the bore, therebypreventing the piston from moving with respect to the actuator housing.14. The method of claim 13, further including applying a voltage to asecond opposing piezo electric device, thereby allowing fluid to flowfrom the bore to release the piston and allow the engine valve to returnto the first position.
 15. The method of claim 13, wherein fluid isallowed to flow from the bore after a predetermined period of time toachieve the desired valve actuation pattern.
 16. The method of claim 13,further including directing a flow of fluid from the bore to anaccumulator.